AN OVERVIEW OF THE GEOLOGY AND GEOCHEMISTRY OF THE TRI-STATES (KS-MO-OK) MINING DISTRICT

The Tri-States Mineral District extends from near Commerce in Northeast Oklahoma through Galena and Baxter Springs, Kansas, eastward to a line that runs from Oronogo south-southeast to near Granby, Missouri. Mineralization in the district is localized in the Keokuk and Warsaw formations. Ore most frequently is associated with chert and jasperoid much of which occurs as jasperoid-cemented chert breccia. Mineralization in the district commonly is associated with folds that result from deep faults, often is located at the intersection of fault trends, and occasionally is localized in the limbs of folds. Zinc-lead ore grade is higher near localized contacts between dolomitize and jasperoid, usually along vertical to near vertical shear and fracture zones. The ages of fault and fracture zones in the district are poorly constrained but likely predate ore emplacement. Sphalerite, galena, and chalcopyrite are the primary ore minerals in the district. Secondary oxidation minerals include smithsonite, hemimorphite, and cerussite. Pyrite, marcasite, calcite, dolomite, and quartz are the principle gangue minerals. In addition, over 25 different metals occur at lower concentrations, often as contaminants in sphalerite and galena, and less commonly as individual minerals. Of these elements, cadmium, germanium, gallium, and indium are found in concentrations ranging from 7,000 ppm (Cd) to 10 ppm (In), primarily as contaminants in sphalerite; however, greenockite (CdS) has been reported in ore in the district. Silver is present in significant quantities as a contaminant in Galena. Early mineralization consists of gray dolomite followed by early sulfide minerals and pink dolomites. Main-stage sulfide minerals precipitated after the deposition of pink dolomite, with sphalerite pre-dating galena. Following main-stage deposition, chalcopyrite and gangue sulfides were emplaced, followed by large volumes of calcite. The deposits of the Tri-States District likely formed due to topography-driven flow moving northward from the Ouachita fold and thrust belt. These fluids derived salinity from evaporites and connate brines, gained heat from the geothermal gradient, and scoured metals from basement rocks and basal arkosic sandstone. Precipitation likely resulted from cooling along fluid-flow pathways.